NavList:

On March 5 (post 12176), I wrote:
"According to that 1897 history, sextant certification work was performed at Kew Observatory from 1862 (with an early heliostat system developed by the famous Francis Galton which, according to his memoirs, due to "the uncertainty of sunshine in our climate proved to be of little practical value) and with greater success using Cooke's collimation system starting in 1869. As noted above the collimation equipment was removed to Teddington in 1910. The sextant room at Kew Obs was a little, dark room in the basement in the southeast corner of the observatory, about 100 square feet, adjoining the caretaker's apartments (starting in about 1884, sextant shades were tested separately, two floors directly above the sextant room). The instrument for testing sextant arc error consisted of "five collimating telescopes, with gas jets behind them, which illuminate objects, in the shape of crosses, situated at the principal foci. The collimators are fixed on a slate slab, carried by brickwork. The emergent beams of light converge to a common centre, and are inclined at certain known angles. The readings given by a sextant for the magnitude of these angles supply the data for determining the error at various points in its arc." Given that this service had been available since the 1860s, it's interesting to read this: "In 1888 the Admiralty made a regulation that all sextants used by cadets of H.M. Navy must be certificated at Kew." That seems like a remarkably late date to put this requirement into effect, but I would imagine that it had a powerful effect on sextant manufacturers. This same history notes that Kew Obs began rating watches (and chronometer watches) in 1884 following "pretty closely" the Geneva system, and that the observatory also rated marine chronometers starting in 1888."

I've found a few other minor details just to add to the story of sextants at Kew. First, there was only a small amount of sextant certification work done before 1880. In the "English Mechanic", G.W. Whipple, then the director of Kew Observatory, wrote an almost plaintive letter in January 1880 stating that sextant calibration apparently didn't matter much to most navigators since Kew had tested ONLY FOUR sextants in the previous twelve months (out of some 5000 scientific or "philosophical" instruments tested all told). I would assume that this was largely because the word had not gotten out that this inexpensive service was available and also because the Royal Navy did not yet require Kew-certified sextants for its cadets. Does anyone have a first edition of Lecky's "Wrinkles"? Of course, he describes exactly how to get a sextant certified at Kew (later Teddington) in later editions, but is there a date when this first appears in navigation manuals and books like "Wrinkles"? Within a decade, Kew was calibrating something on the order of a thousand sextants annually. The whole idea of calibrated sextants with certificates in the case apparently really got going in the 1880s.

Also, on a minor note, since I mentioned the location of the sextant room from the 1897 article above, it turns out that the calibration apparatus was moved to another tiny room, the neighboring "pendulum room" (also in the basement), in 1885 due to increased demands for its use. Maybe the sextant room was overflowing with the hundreds of instruments they were testing by that date.

One other bit of trivia: while the sextant work was supposed to be transferred to Teddington in 1910, the sources I've found suggest it didn't happen until as late as 1913 due to labor strikes and other practical difficulties.

I also wrote in that post:
"Today it seems that the observatory is generally known as "King's Observatory" again. If you would like to see it in its current setting, go to Google Maps or similar at these coordinates: 51.4689 N, 0.314159 W (just seeing if anyone's paying attention). You will discover that it is smack in the middle of the Royal Mid-Surrey golf course."

And apparently no one is paying attention. ;-)

-FER

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